iPhoto is clumsy when you're using Lightroom.
That's because iPhoto and Lightroom are databases.
They can't "talk" to each together.
Therefore, there's no easy way to use both.
There are two options below.
Read about them and choose the one that fits your needs.
Your photographs are stored in the iPhoto Library folder.
This folder is a package-content folder.
It's an Apple-only folder.
Non-Apple programs can't open the folder.
Therefore, you have to "jailbreak" your photographs from this folder "jail."
Backup the photographs you have in iPhoto by exporting them.
The exported photographs won't be organized into Events.
However, you'll have your photographs in case one of the programs you're using does something dastardly.
In iPhoto, do the following.
1) Go to File > Export.
2) Select Original in the Kind menu.
The unedited files will be exported.
4) Click Export.
5) Select the destination folder.
Before you perform an action on thousands of files, experiment with just a few.
phoshare . . .
. . . allows you to export and synchronize your iPhoto library to a folder tree.
It preserves both the original and modified image, your event and album organization, and applies your iPhoto titles, descriptions, keywords, face tags, face rectangles, places, and ratings to the IPTC/EXIF metadata of your images.
You can export a full copy of your library, or just build a tree of linked images that require very little additional disk space.
You can re-run phoshare at any time to synchronize any changes made in iPhoto to your export tree quickly.
phoshare works well with file-system based photo management tools like Picasa, Adobe Bridge, or Windows Live Photo Gallery.
phoshare was created by Tilman Sporkert, who works at Google.
I like managing and editing my photos with iPhoto, but I don't like having my work kept hostage inside iPhoto.
I also like Picasa from Google . . . And sometimes I feel like using Adobe Bridge.
So it's important to me that any work I invest into my photo collection (edits, organization, annotations, tagging) is not tied up in one application.
That's where phoshare comes in.
Whether you need to backup your photos or movies to an external hard drive (in a non-proprietary format and possibly including iPhoto metadata) or just want to export your photos or movies for use in other applications, iPhoto To Disk makes it easy.
The answer by teamrusnac below in an Adobe-Lightroom-forum thread describes using Aperture to get your photographs out of iPhoto.
You can download a free trial of Aperture to do so.
The method below was adapted from Moving Your Images From iPhoto to Lightroom by Gene McCullagh.
The method has the advantage of only needing the programs you already have, iPhoto and Lightroom.
The disadvantages are that:
• Keywords, tags, and captions, are not transferred.
• Events that you create must be transferred manually, one at a time.
iPhoto keeps your original files in a folder called Masters.
You'll import the files from the Masters folder.
When you edit a file in iPhoto, the edited version is saved to a folder called Modified.
If you want to keep the edited versions, you'll import them from the Modified folder.
• Created by iPhoto when you import photographs.
• Real folders in the iPhoto Library.
• Are based on the date you took the photographs.
Albums are created by you.
Let's say you created an album called Galapagos.
There's no real folder called Galapagos containing your photographs.
The albums you created are virtual.
They exist only in the iPhoto database.
The Galapagos photographs are in the Masters folder created by iPhoto when you downloaded the files from your memory card.
So, if you want to preserve the Galapagos album, you'll export it from iPhoto to your Desktop.
From the Desktop, you'll import the album into Lightroom.
The EXIF metadata (date, time, exposure, etc.) will accompany your iPhoto files on their trip to Lightroom.
That's because EXIF metadata is part of the JPEG file.
IPTC metadata (keywords, tags, captions, etc.) won't transfer because iPhoto stores this IPTC metadata separately from the JPEG files.
Do the following.
1) Go to Finder > MacIntoshHD > Users > Pictures > iPhoto Library.
Clicking iPhoto Library will simply open iPhoto.
Instead . . .
2) Right click the iPhoto Library.
Can't right click with your mouse?
Press and hold Ctrl, and click your mouse button.
3) Click Show Package Contents.
You're in the iPhoto Library.
The important folders are Masters and Modified, mentioned above.
The files in these folders are arranged as follows.
Year > Month/Day/Year
4) Right click on the Masters folder, and click Make Alias.
An alias is a shortcut to something, in this case, the Masters folder.
5) Drag the Masters alias to your Desktop.
6) Open Lightroom and click Import in the lower-left corner.
7) On the left side of the Import window, do the following.
a) In the top-left corner, click Select a source.
b) Click Other Destination.
c) Navigate to the Desktop and click the Masters alias.
Lightroom now knows where to get the files.
8) Lightroom now needs to know whether to copy or move the files.
At the top of the Import window, select Copy.
The files will be copied to a new location, and will be added to your Lightroom catalog.
If you were to select Add, Lightroom wouldn't be able to get to the files hidden in the iPhoto Library.
If you were to select Move, iPhoto would be emptied of its files.
You want to keep iPhoto as it is for a while.
So, again, select Copy.
9) By default, Lightroom will copy the files to a folder called Masters in Pictures.
You may want to import the files into a folder called From iPhoto, for example.
Pictures > From iPhoto > Masters
10) Click Import in the lower-right corner.
Repeat the above steps, but with the Modified folder instead of the Masters folder.
Pictures > From iPhoto > Modified
As described above, the albums you made in iPhoto are virtual.
There's no folder in the iPhoto library full of the photographs that are in the albums that you created.
Do the following.
Let's say to created an album called Granny Drinks a Smoothie.
1) Create a folder on your Desktop called Granny Drinks a Smoothie
2) Open the Event that you created, Granny Drinks a Smoothie.
3) Export the photographs in the Event to the Granny-Drinks-a-Smoothie folder.
4) Import the Granny-Drinks-a-Smoothie folder—that's on your Desktop—into Lightroom.
5) Create a collection called Granny Drinks a Smoothie.
iPhoto stores the IPTC metadata separately from the JPEG files.
Savvy computer users can use ExifTool to write the IPTC metadata to their JPEG files.
ExifTool by Phil Harvey . . .
. . . is a platform-independent Perl library plus a command-line application for reading, writing and editing meta information in a wide variety of files.
Use this method if you want to import some of your photographs from iPhoto to Lightroom.
Do the following.
1) In iPhoto, export the photographs to your Desktop.
2) In Lightroom, import the photographs.
3) If you want to return the edited photographs to iPhoto, rename the files.
Append -LR-edited to the file names.
4) In Lightroom, export the photographs to your Desktop.
5) In iPhoto, import the photographs from the Desktop.
The edited photographs will appear in an Event with today's date.
The original photographs are in an older Event.
You can merge the edited photographs with the original photographs, if you wish.
Drag the new Event onto the Event in which the original photographs are located, to merge the two.
Go to View > Sort Photos > By Title.
The masters and edited photographs will be side-by-side.